Data centers route massive quantities of data. Currently, data centers may have a throughput of 5-10 terabytes per second, which is expected to increase in the future. Data centers contain huge numbers of racks of servers, racks of storage devices, and other racks often with top-of-rack (TOR) switches, which are interconnected via massive centralized packet switching resources. In data centers, electrical packet switches are used to route data in these data centers. However, electrical packet switches have capacity limitations.